Mounting of bifocal lens blanks



F. D. KINNEY MOUNTING 0F BIFOCAL LENS BLANKS Nov. 26, 1940.

Filed Oct. 50, 1936 4 Sheets-Sheet 1 INVENTOR PH) 0- K/NNEY BY 5 flaw Nov. 26, 1940. KlNNEY 2,223,214

MO NTING 0F -BIFOCAL LENS BLANKS 4 Sheets-Sheet 2 Filed Oct. 50, 1956 INVENTOR QHYD. KIN/YE? X Nov. 26, 1940. F. D. KINNEY MOUNTING OF BIFOCAL LENS BLANKS Filed Oct. 30, 1956 4 Sheets-Sheget 3 FIEIHV .INVENTOR 139) D K INNE Y W Nov. 26, 1940. F. D. KINNEY 2,223,214

MOUNTING OF BIFQCAL LENS BLANKS Filed 001;. 30, 1936 4 Sheets-Sheet 4 INVENTOR am D. .K/N/ E? Patented Nov. 26, 1940 UNITED STATES 2,223,214 MOUNTING 0F BIFOCAL LENS BLANKS m n. Kinney, Southbrl American Optical Company,

we a voluntary association of Massachu- Application 0mm so. 1936, Serial No. loss-1s 13 Claims. (01. 51-217) This invention relates to the-generation 'of a surface of the proper curvature on a bifocal.

lens, and more particularly to the mounting of the work-piece in preparation for the grinding and polishing operations.

An object of the invention is to improve the procedure 'to be followed in mounting the workpiece for the grinding of the segment side so that a segment of correct size and shape may be produced a finished bifocal lens;

Figs. III and IV are corresponding views through a disc having a segment fused thereon;

Fig. V is a diagrammatic plan view of a bifocal lens illustrating the change, in area of the se ment as grinding proceeds;

Fig. V1 is a view principally in central vertical section of my improved blocking holder;

Fig. VII is a plan view of the seat for the lens and the adjustable mechanism for contacting and positioning the lens on this seat, the view being taken on the line 1-1 of Fig. VI;

Fig. VIII is a face view of a glass target employed in centering a lens blank on the seat;

Fig. IX is a diagrammatic view illustrating the relation between the bifocal lens blank and the target of Fig. VIII;

Fig. X is a face view of a bifocal lens blank which must be positioned so as to avoid decrease in width of the segment;

Fig. X1 is a face view of a modified form of target suitable for positioning a lens blank such as shown in Fig. x;

Fig. IE1 is a view in elevation of a lens blocking device; I v I Fig. XIII is a view in side elevation of this device looking from the right of Fig. X[I, part of the adjustable positioning mechanism for the lens being broken away;

Fig. XIV, is a sectional view through the lens and lens support, this section being taken on the same axis as that of the spindle of the lens blocking device of Fig. XIII;

Fig. XV is-a view partly in side elevation and partly in vertical section on the axis of the needle valve, showing one of the pots of the blocking device of Fig. XIII;

Fig. XVI is a view similar to Fig. XIII, illustrating the step of embedding the lower end of a spindle in a portion of the support for the lens;

Fig. XVII is a diagrammatic view illustrating the subsequent grinding of the lens blank;

Fig. XVIII is a view similar to Fig. XIV showing a modified form of lens support; and

Fig. XIX is a view similar to Fig. x showing a modified form of bifocal lens blank.

The present invention is applicable to the production of bifocal lenses of various types, such as Ful-Vue, Panoptik, Kryptok, and others well known in the art.

In the production of such lenses a segment is fused to a major lens blank and the segment side of the blank ground to obtain the proper size and shape of segment. The common practice in grinding away the excess glass of such bifocal lenses at the present time isto control this operation manually. This requires considerable skill, and since trained operators must be paid high wages, the process is a costly one. Moreover, since there is a human factor in this mannerof producing bifocal lenses, it is difllcult to insure uniform high quality.

Accordingly, an object of my invention is to provide an improved method and apparatus for blocking bifocal lens blanks so that when the segment side of bifocal lenses is finished a se ment of more uniform shape and size results, while at the same time the requirements for skill on the part of the operators and for supervision of their work are lessened.

In order to insure that during the process of generating a surface of the proper curvature on the segment side of the lens blank equal amounts of stock shall be removed from each side of the blank segment, I carefully block the blank so that a predetermined center of the segment (which is to be the center of the reading field) is accurately positioned on the axis about which the blank is made to rotate in generating the desired surface, and so that the same axis is normal to the countersink curve and the segment fused thereon. I

It will be noted that the positioning of the blank depends upon the countersink curve on which the button is fused and the geometric center of the button, but is not governed by the other features of the blank.

I will give a specific example in connection with Figs. I to V inclusive, the product which it is intended that the grinding and polishing shall produce, namely, a finished bifocal lens 20, being shown in Figs. I and II, and the blank 2i being shown in Figs. III and IV. The blank comprises a'major portion 22 having a countersink curve 28 and a composite button 24 fused rotation of the blank during grinding, and that the same axis is normal to the countersink curve 28, then as grinding proceeds the area of the segment will diminish in the manner indicated' by the arrows a, b, and c in Fig. V. The important factor is that equal amounts of stock will be removed from each side and from the bottom of the segment 29.

Assuming that the rough segment size is 24 by 16 millimeters, then one millimeter will be removed from each side, and one millimeter will be removed from the depth of the segment, so that in the resulting lens the segment will measure 22 by 15 millimeters.

Furthermore, the process may be so carried out that a segment 2 millimeters smaller is generated, the dimensions 20 by 14 millimeters being a desirable size and proportion ior Ful-Vue biiocals.

This procedure overcomes to a large extent the objections to the prior practice due to inherent errors arising out of the eccentric blocking of lens blanks. If the lens blank is so blocked that the predetermined center of its segment 25 is lightly eccentric with respect to the axis of rotation of the blank, and so that the axis on-which it rotates during grinding is not normal to the countersink surface 29, the resulting segment is not of the right proportions. This is due to the removal of unequal amounts of stock from the two sides of the segment, resulting in incorrect proportions. It is furthermore possible that under such conditions the depth would also be incorrect.

Under the present practice of controlling the grinding manually, these defects arise so as to throw the segment out of proportion; and it requires skilled manipulation by the operator, by using an eccentric mechanical holder, to correct the error. This is known as a-pulling operation.

As a means of insuring exact blocking, I have devised a novel blocking holder such as shown in Fig. VI. This holder comprises a base 21 in which is positioned a tubular mounting member 28. The upper portion of this member 28 is tapered to fit within a corresponding recess in the seat 29 for the lens blank. The opening 89 within the seat 29 forms a continuation of the central opening in the tubular member 28; and light from a source II in the tubular member 28 passes upwardly through a glass target or screen 32 positioned in the opening 89 and lying beneath the segment 29 of the lens blank when the latter is on the seat 29. A pin 84 projects from the member 28 to enter a recess in the lower rim of the seat 29 to orientthe latter ready to receive a lens blank. Three prongs or contacts 85 project upwardly from the seat 29; and the countersink surface 28 of the major lens blank rests on the tips of these contacts 85, so'that If the fused the lens blank is supported solely on these three tips. The latter are accurately positioned so-that as the lens blank is moved about in positioning it relative to the seat 29, the axis of the seat (and mounting member 28) is constantly normal to the countersink surface 28 provided the contacts 89 do not move oi! the countersink surface 28.

I provide means engageable with the lens blank for adjusting the position of the lens blank on the seat 29 relative to the screen 82. I have illustrated as a preferred embodiment a member 89 supported on top of a flange 81 formed integrally with the seat proper 29. The member 89 carries a spring pressed plunger 89 which engages the rim of the lens blank on one side, and an abutment 49 which engages the rim of the lens blank on the other side. A set screw 4| is provided for increasing or decreasing the tension of the spring which pushes the plunger 89 against the lens blank; and pins 42 and 48, carried respectively by the member 89 and the plunger 89, permit the operator to retract the plunger 89. The abutment 40 positively positions the lens blank relative to the member 89,

and the latter may be moved about on the flange 81 to bring the lens blank to the desired posi-' tion relative to the screen or target 82.

An arm 45 carried by the base 21 supports an eye-piece 49 for assisting in aligning the lens blank with the screen 82. The screen 82 is preferably a glass target which has etched on its face appropriate markings for determining-the proper position for the above referred to dividing line 29 and the predetermined center. The target shown in Fig. VIII has crossed lines-indicating the proper position for the predetermined center and a curved line 41 of the same radius as the dividing line 29 on the segment and at the proper distance from the predetermined center of the segment.

The eye-piece 49 is provided with a sight hole 48 which is the predetermined distance away from the axis of the seat 29 and directly over the line 41 of the target. The illumination from the source 8i makes the line 41 on the target more pronounced. The manner in which the target assists in properly positioning the lens blank is indicated in Fig. xx, in which the target line 41 has been brought into coincidence with the dividing line 29 of the segment. When this has been accomplished and the segment has been centered on the cross lines the member 89 is clamped to the flange 81 by a nut 58 threaded on the body portion oi the seat 29. A lever 54 projects from the nut 58; and when the desired coincidence has been obtained by sliding the member 89 on the flange 81 to the proper position, the lever 54 can be rotated to tighten the nut 58 and" clamp the member 89 to the flange 81.

For some types of lenses it is desirable to have in addition to a line 41a for positioning the dividing line on the segment, the end lines 59 at the two ends or the line 41a, as indicated in Fig. XI. Such a target 82a is particularly useful in positioning a bifocal lens of the Panoptik type, such as illustrated in Fig. X, which comprises a major lens blank 99 and a composite button 91 of which the portion 58 is to constitute the minor lens or segment of the bifocal lens. The lines 99 of the target 8211 assist in properly positioning the two ends of the segment 58. The extent of the segment after grinding is indicated by, the broken line 59.

a,2as,a14 3 A target of the type shown in Fig. XI is furthermore of advantage in positioning a bifocal.

lens blank such as illustrated in Fig. XIX, which comprises a major lens blank 88a and a com- 5 posite button 810 of which the portion 88a is to constitute the minor lens or segment of the bifocal lens. The lines 88 of the target 8241 assist in prop'eily positioning the two ends of the segment 58a. It will be noted that edge portions 512' and 513, so that the three prongs or contacts 85 may engage the countersink surface of' the major lens blank 880..

With the aid of the end lines 58 on-the target 82a, the geometric center of the segment is brought into accurate coincidence with the axis of rotation of the blank. The line 81 or the line 41a alone gives quite accurate positioning if the dividing line (such as indicated by 28 in Fig. III) is made to register therewith and the contacts 85 are all three maintained in engagement with the spherical countersink surface (such as indicated by 28 in Fig. III); If the eye of the operator is not true enough to center the segment without the end lines 88, the-only inaccuracy which results is the grinding of a slight prism in the segment; and the proportions of the segment will neverthelessbe correct if the registry with line 41, as above referred to, is 80 maintained.

With the aid of the screen or target positioned in the opening 88 in the seat 28, the operator I has now accurately positioned the lens blank and has clamped the positioning member 88 to the seat proper by means of the nut 82. The seat mounted in the blocking device shown in Figs.

XII, XIII, and XVI. A tapered mounting mem- 40 her 88 carried by the base 8| of the device is formed to so fit thetrecessin the seat 28 as to position the seat on the axis of this device. A standard 82 is carried by the base 8|, and this standard provides a pair of bearings 88 and 84 in which a spindle 85 is vertically slidable on the above mentioned axis of. the device. v

The lower end of the spindle 85 is tapered to flt within a socket member 81 from whose lower end extends a stem 88 terminating in a head 88. This head may be in the form of a hex nut threaded on to the lower end of the stem 88. The head 68 is received within a recess or chamber ID in a lens support II. A compression spring 12 coiled about thestem 88 and extending between the socket member 81 and the lens support Hurges the latter away-from the socket member so as to tend to withdraw the stem 88 from the lens support II. The opening in the lens support 1| through which the stem 88 extends is large enough so that there is no binding, and the lens support is free to movev and A modified form of lens support Ila is illustrated in Fig. XVIII. The duct 18a leads into a 7 central chamber 18a which is not only large enough to freely, accommodate the head 68 on the stem 68, but furthermore opens through the bottom of the lens support, so that molten metal,

poured in through the duct 184 forms the central portion of the support for the lens blank.

This opening is surrounded by the lower ri portion ll of the lens support.

The spindle 85 is raised and loweredby means 1 of a lever 18 .cpnnected to the spindle by latof the set screw is adapted to engage the top 10 of the standard 62 to limit downward movement of the spindle 65. On the standard 82 are mounted, by means of brackets 88, two swinging supports 86, one carrying an electrically heated receptacle or pot for the molten substance 15 such as the low melting point alloy above referred to, and the other carrying an electrically heated receptacle or pot 88 for depositing cement or other adhesive material on the top surface of the lens blank. The two receptacles 81 and 88 20 are substantially alike, and therefore description of the receptacle 88 in connection with the sectional view of it in Fig. XV will sufll ce for the two.

The receptacle proper isprovided with a cen- 85 tral trough 88, into which the rest of the material in the receptacle will drain: and this trough slopes to an outlet 8|, which is preferably of a hard, heat resisting material, such as stainless steel. A bracket 82 on the opposite side of the receptacle from the outlet 8| pivotally supports a lever 88 which has a thumb rest-84 in convenient relation to a handle 85 on the pot 88, so that the operator in grasping the handle 88 for swinging the receptacle,- may rest his thumb 88 on the rest 84. The handle 85 on the receptacle extends forwardly so asto be readily grasped by the operator. A coil spring 81 interposed between the thumb rest 84 and the handle 88 urges the rest away from the handle. Each recep- 40 tacle is so mounted that it can be swung conveniently into position (compare Figs. XIII and XVI for discharging cement, or molten metal according to requirements).

The other end of the lever 88 is connected by 45 adjustable abutments 88 and 88 to the upper end of the rod I88, which acts as a needle valve within the outlet 8|. Setscrews l8l provide for the adjustments of the abutments 88 and 88, and the latter are rounded so as toavoid binding against 50 the lever 83 as it is swung about its pivot.

So far as I am aware, the subject matter of the present application involves not only novel principles of construction of a lens blocking device, but also a novel procedure for mounting a 55 lens blank on a support in preparation for grinding.

In the common method of mounting a len blank, the latter'rests upon a mass of pitch of sufllcient thickness to allow when plastic for the go precise setting of the lens blank. According to my teaching a lens support floats relative to the spindle which carries-it, until the lens support has conformed in position to the surface of the lens blank, and a plastic substance is pro- 55 vided for fixing the lens support in the position which has thus been determined. Suitable adhesive material such as pitch may be employed to cause the lens blank to stick to the lens support. In otherwords, the blocking may be con- 70 sidered to be a step removed from the lens blank itself, and that it is thelens support which is blocked instead of the lens blank itself. Since the lens blank has already been accurately positioned and centered relative to the axis about u seat 29. According to the broader aspects of my,

invention, it is immaterial whether such accugas use

which the blank is to rotate during grinding and polishing, the plastic substance above mentioned permits the lens support to take a position which is determined by the lens blank rather than vice versa, and when the plastic substance hardens, the lens blank is fixedly mounted on the desired axis. This is brought out more clearly by a statement of the method by which is followed in accordance with the present invention in mounting a lens.

The lens blank is accurately positioned on a rate positioning be accomplished by means of a separate instrumentality, or while the seat is mounted on the blocking device itself. With the apparatus disclosed in the drawings I have found that more accurate results are obtained by employing the blocking holder illustrated in Fig. VI, for positioning the lens blank asa preliminary operation. Y

With the lens blank accurately positioned on its seat, the lens support is capable of assuming a position in conformity therewith because of the loose fit of the stem 68 and head 69 in the support II or Ila. With the bottom surface of the support II, or the bottom of the rim ll of the support Ila lying against the lens blank under pressure from the lever I5 transmitted through the spring I2, the operator fills the chamber I or 10a with the fluid material from the recep tacle 81 through the duct 13 or 13a. The support 'II is particularly useful where a large number of lenses are to be mounted having a surface ofthe same curvature. Thus the bottom of the support may be given this curvature, and if an application of adhesive material such as pitch is made from the receptacle 88 on the upper surface of the work-piece before the support 'lIis lowered, the work-piece is affixed to the support under the pressure of the spring I2 while the head 69 is being embedded in the material poured into chamber I0. I

The support Ila provides automatic reforming of its contour to correspond to tht curvature of the lens blank being blocked, inasmuch as the central portion of the bottom surface of the support is not permanent in character, but is filled in each time as will now be explained.

A coating of adhesive material is applied to the upper surface of the lens blank, a suitable material being a mixture of guncotton and the synthetic resin sold under the trade name Binsol in suitable solvents and/or plasticizing agents.

I prefer to use a mixture of guncotton, Binsol,

alcohol, dibutyl phthalate, and toluene. Against .the adhesive coated surface of the work-piece is pressed the rim I4 of the support Ila. As the lens blank is accurately positioned on its seat, it is in the proper relation to the axis of the spindle 65 as the latter is lowered by bringing the lever I5 down; and the floating connection of the support Ila to the spindle 65 permits the ofthe support II or 'IIa as the case'may be. This of course effects the rigid mounting of the lens blank on the socket member 61 in the desired relation to the axis of the latter. The tightening screw 4| may now be released and the spindle 65 raised, carrying with it the support and the lens blank firmly attached to/ The subsequent grinding ope fifin, which is the work-piece, that is, the lens blank. The.

latter is rotated by means of a pulley IIO which drives the taper spindle I05. The latter is surrounded by a non-rotating sleeve III, which is so connected to the spindle I05 as to cause the latter to follow the axial movements of the sleeve III. This can of course be effected by providing collars on the spindle I05 against which the sleeve I may abut. The sleeve III is urged upwardly by having rack teeth II2 thereon with which a pinion Il3 meshes. A weight Ill on a lever arm I I5 which is connected to the gear II3 tends to lift the sleeve III, and therefore the taper spindle I05.

The weight Ill lowers as grinding continues, and the excess stock is removed evenly so that the segment is reduced in the manner indicated by .the successive steps a, b, and c of Fig. V. An adjustable stop H6 permits the operator to predetermine the amount of glass removed so that the grinding operation is to a considerable extent automatically controlled. This is made possible in .the first place by the accurate blocking of the lens blank so that an even amount of glass is removed from all portions of the segment.

Such automatic control is furthermore made possible by the arrangement which makes it possible to'block the blank to a predetermined height. In other words, the stop 8| determines the exact position of the socket member 61 with relation to the side of the lens blank onwhich the segment is fused. This relation is always the same, since the stop- 8| and the seat 29 for the lens blank bear a constant predetermined relation, and any inequalities in the lens blank are taken up in the process of embedding the head 60 in the recess 10 in the lens support 'II or Ila.

The principal advantage of the present invention is that it makes it possible to produce a segment of more uniform shape and size with a minimum amount of effort and supervision, the need for highly skilled labor being eliminated. The invention makes it a comparatively easy matter to block the lens blank so that the predetermined center of .the segment is positioned concentrically on the axis upon which the blankwill rotate during subsequent grinding and so that that axis will be normal to the countersink curve on which the segment is fused. As a result the invention affords the distinct advantage that the segment is proportionately reduced in size on both sides and on the bottom, resulting in a segment of correct size and shape.

Important advantages of my invention arise through the use of the socket member 61 and head 69. This novel construction with the fioat- I of variable thickness. This construction moreover has the advantage that the operator may block these blanks to a fixed height measured from the skirt of the recessed member 01 to the countersink curve 23, this height being independent of prism or thickness of blank. Without such an arrangement for blocking the bifocal lens blank to a predetermined height, it would be impractical to grind the bifocal side of the the drawings are for purposes of illustration only,

and since the steps of the method as described for mounting a blank in preparation for generating a surface thereon need not be followed rigorously and in particular may be varied as to sequence, it will be understood that the invention may be otherwise embodied and practised within the scope of the following claims, and it will furthermore be understood thatno method claim is limited to the sequence in which the steps are stated therein unless specifically required by that claim.

I claim:

1. In a method of blocking a bifocal lens blank in preparation for generating a surface on the segment side thereof, the steps consisting in supporting a lens blank by a support engaging the countersink curve of the blank, aligning a point at which the optical center of the segment is to be located with the axis of rotation of a two-part block adapted to be rotatably mounted for generating the desired surface on the segment side 7 of the blank, attaching one part of said block to the opposite side of the blank and rigidly uniting 45 the parts of said block while maintaining said support in engagement with the countersink curve of the blank and the axis of rotation of the two-part block in alignment with the point at which the optical center of the segment is to be located.

2. In a method of blocking a bifocal lens blank in preparation for generating a surface on the segment side thereof, the steps consisting in supporting a bifocal lens blank by a support having contacts for engaging the countersink curve of the blank, adjusting the position of the blank on said contacts so as to align a point at which the optical center of the segment is to be located with the axis of rotation of a two-part block adapted to be rotatably mounted for generating the desired surface on the segment side of the blank, attaching one part of said two-part block to the side of the blank opposite the segment and rigidly uniting the parts of said block while yieldably urging the attached part of said block and the blank toward said contacts and while maintaining the axis of the other part of said block in alignment with the point at which the optical center of the segment is to be located.

3. A method of blocking a lens blank in preparation for generating a surface thereon comprising locating and holding the lens blank in desired angular and centering P ition with respect to the axis about which it rotates during surface generation, applying adhesive material to the surface of the lens blank opposite that to be generated, yieldably pressing one end of a hollow support member, adapted to loosely receive an end portion of a spindle member in its other end. against said opposite surface so as to cause said hollow support member toconform to said angular position of said lens blank, and embedding said spindle end portion in said hollow support member by pouring molten material into said hollow portion on said lens blank and permittin said molten material to solidify by cooling whereby said spindle member and said hollow support member achieve the same angular relation as exists between said lens blank and said surface generation axis of rotation.

4. A blocking device comprising a supporting member, a lens block loosely connected to said supporting member having a surface for adhering to a-surface of a lens blank, said supporting member being movable to advance said'lens block along a given axis about which the block is adapted to be rotated during the abrading of the blank,

an aligning device having a seat for receiving the lens blank, said seat having centering means for locating a predetermined point on'the blank on the center of said seat, means for mounting saidaligning device on said blocking device with the center of said seat in axial alignment with the longitudinal axis of the support carrying the lens block with themovement of said support and block towards the lens blank along said longi tudlnal axis being adapted to move the block into engagement with the lens. blank to cause said block to tilt into conformity with the engaged surface of-the blank through its loose connection' with its'support, and means for securing the block to the lens in said relation and for also securing the block in rigid relation with its support.

5. A lens blocking device comprising a lens block, means for advancing said block along the axis about which it rotates during-surface gen-.

eration, a holder having a seat for a lens blank thereon. said holder having an opening and a target screen ln said opening and a portion for gripping said lens blank adapted to be moved with said lens blank whereby a predetermined point on the lens blank may be located in registry with the center of said target screen, means for mounting said holder and said predetermined point on said blank in axial alignment with the longitudinal axis of the lens block advancing means, said holder being capable of being removed from its mounting means and returned to and interfltted therewith so as to restore said alignment of said holder with the axis of said advancing means.

6. A lens blocking device comprising a support having a member reciprocally mounted thereon, a lens block connected to said member by a universal connection including yielding means, said reciprocally mounted member and block being movable along an axis about which the block is to be rotated during surface generation, an aligning device having a seat for receiving saidlens blank, said aligning device having centering means whereby a predetermined point on said lens blank may be centered with said centering means to rotate the blank in desired relation with said seat and means for retaining said blank in said relation and means for mounting said seat and the lens blank carried thereby in axial alignment with the reciprocal member to be engaged by said lens block with the predetermined point of the lens blank in axial alignment with the longitudinal axis of the reciprocal member.

"I. A lens blocking device comprising means for locating and holding a lens blank in predetermined position, a member having a portion movable in a controlled direction, a lens block mounted on said movable portion by a connection permitting tilting of the lens block relative thereto and being movable about an axis substantially normal to the plane of the lens blank to bring said block into engagement with said lens blank to cause said block to tilt into conformity with the surface of said blank and means for applying molten material to said connection which material upon hardening fixes the block against movement relative to said member.

8. A lens blocking device comprising means for supporting a lens blank in a'given position, a support mounted on said device for movement toward and away from said lens blank along an axis passing through a predetermined point on said blank about which the blank is to be rotated during abrading, said support having a lens block loosely connected thereto and adapted to be moved by said support into engagement with the blank so as to cause it to tilt into conformity with the engaged surface of the blank, and means for securing said blank to said block and means for fixing said lens block against tilting movement relative to its support. 1

9. A method of positioning and fixing a work piece on a two-part support in preparation for generating a surface thereon comprising attaching the work piece to one-part of said support by means fixing it against movement relative to said part while maintaining the other part in freedom of movement angularly relative to the work piece, adjusting said other part to desired angular relation with said work piece and fixing the parts of said support together in saidadjusted position by embedding a portion of one of the parts in a low melting point-substance carried by the other part. I

10. A method of blocking a lens blank in prepartion for generating a surface thereon comprising accurately, positioning thelens blank in desired relation to the axis of a lens block support adapted to be rotated for generating a surface on the said lens-blank, eifecting relative movement between the lens blank and said support so as to cause the lens block-carried by said support to conform to the surface of the lens blank without changing the relation between the lens blank and said axis, making the lens block rigid with the lens blank while the latter is accurately positioned, and rigidly connecting said lens block to said support, also without changing the relation between the lens blank and said axis. 7

11. A lens blocking device for blocking a lens having a countersink recess and a projecting portion, said blockingdevice comprising a holder having a seat with a recess for receiving the projecting portion of the blank with the countersink surface engaging said seat, a target screen in said recess, means engageable with the lens blank adjacent the periphery thereof for adjusting the position of said blank on said seat and means for clamping said means engageable with the lens blank in adjusted position and an eyepiece arranged to focus on said screen so as to aid in adjusting said lens blank to desired aligned position relative-to said target screen.

12. A method of blocking a lens blank in preparation for, generating a surface thereon comprising accurately positioning the lens blank in desired relation to the axis, of a lens block support adapted to be rotated for generating a surface on said lens blank and on which a lens block is yieldably supported, causing the lens block to tilt relative to said support into conformity to the cool and harden.

- FAY D. KINNEY. 

